Genesis of carbonate aggregates in lamprophyres from the northeastern Transdanubian Central Range, Hungary: Magmatic or hydrothermal origin?

Abstract

Carbonate aggregates in Late Cretaceous lamprophyre dikes of the northeastern Transdanubian Central Range (TCR) in Northwest Hungary have been classified into three genetic groups. Type-I dolomite + calcite ± magnesite aggregates have petrographic and geochemical features similar to ocelli described by other workers. Fluid inclusions in Type-I aggregates homogenize between 77 and 204 °C and are of hydrothermal origin. Type-II aggregates are characterized by a polygonal shape and are mostly dolomite. Based on their shape and primary fluid inclusions which homogenize between 95 and 172 °C, these carbonate aggregates are interpreted to fill vugs produced by the dissolution of olivine phenocrysts. Type-III carbonate aggregates show an irregular to polygonal shape and distinct compositional zonation and contain secondary aqueous fluid inclusions. Homogenization temperatures of fluid inclusions are below 104 °C, and zonation patterns suggest partial recrystallization. These carbonate aggregates are most likely xenoliths and xenocrysts from the wall rocks of the lamprophyre melt conduits.